Income Taxes (Schedule Of Deferred Income Tax Assets And Liabilities) (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Current [Member]
Deferred Tax Assets And Liabilities [Line Items]
Accruals not currently deductible	$ 3,721,183	$ 2,465,349
Stock based compensation	12,044,953	8,730,729
Other assets	5,690,130	4,874,704
Total deferred income tax assets	21,456,266	16,070,782
Other liabilities	(527,417)	(327,490)
Net deferred income taxes	20,928,849	15,743,292
Non-Current [Member]
Deferred Tax Assets And Liabilities [Line Items]
Accruals not currently deductible	186,997	152,716
Stock based compensation	1,696,966	1,473,236
Impairment loss on available-for-sale securities	327,308	471,401
Other assets	3,609	3,809
Total deferred income tax assets	2,214,880	2,101,162
Excess tax over book depreciation	(47,704,521)	(41,681,342)
Patent costs	(8,137,111)	(5,606,595)
Unrealized gain on investments	(3,146,585)	(3,027,206)
Net deferred income taxes	$ (56,773,337)	$ (48,213,981)